US4556831A - Circuit arrangement for electrical tool with clutch - Google Patents

Circuit arrangement for electrical tool with clutch Download PDF

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Publication number
US4556831A
US4556831A US06/629,869 US62986984A US4556831A US 4556831 A US4556831 A US 4556831A US 62986984 A US62986984 A US 62986984A US 4556831 A US4556831 A US 4556831A
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US
United States
Prior art keywords
state
circuit
limit switch
motor
capacitor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
US06/629,869
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English (en)
Inventor
Junshin Sakamoto
Shigeru Shinohara
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Koki Holdings Co Ltd
Original Assignee
Hitachi Koki Co Ltd
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Filing date
Publication date
Application filed by Hitachi Koki Co Ltd filed Critical Hitachi Koki Co Ltd
Assigned to HITACHI KOKI COMPANY, LIMITED 6-2, 2-CHOME, OOTE-MACHI, CHIYODA-KU, TOKYO, JAPAN reassignment HITACHI KOKI COMPANY, LIMITED 6-2, 2-CHOME, OOTE-MACHI, CHIYODA-KU, TOKYO, JAPAN ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: SAKAMOTO, JUNSHIN, SHINOHARA, SHIGERU
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Publication of US4556831A publication Critical patent/US4556831A/en
Anticipated expiration legal-status Critical
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B45/00—Hand-held or like portable drilling machines, e.g. drill guns; Equipment therefor
    • B23B45/008—Gear boxes, clutches, bearings, feeding mechanisms or like equipment
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
    • H02P29/0016—Control of angular speed of one shaft without controlling the prime mover
    • H02P29/0027—Controlling a clutch between the prime mover and the load

Definitions

  • This invention relates generally to electrical tools such as powered screw drivers, impact wrenches or the like, and more particularly to such tools having a clutch.
  • Conventional electrical tools used for driving screws, nuts or the like have a clutch interposed between a motor shaft and a driven shaft connected to a bit so that a desired tightening torque is obtained with the adjustment of the force of a coil spring or the like. More specifically, such a clutch is used for terminating the transmission of the rotational force from the motor through disengagement thereof when the tightening torque exceeds a predetermined value. Furthermore, a limit switch associated with the clutch is used for triggering a self-holding switching circuit so that both terminals of the motor are short-circuited for effecting dynamic braking. As a result, the motor is stopped. At the time of motor stopping, the clutch is usually put in engaged state again due to rotational inertia. However, the clutch sometimes remains in disengaged state.
  • the present invention has been developed in order to remove the above-described drawback inherent to the conventional circuit arrangements for electrical tools with a clutch.
  • an object of the present invention to provide a new and useful circuit arrangement for an electrical tool with a clutch so that the motor of the tool can be restarted irrespective of the state of the clutch.
  • a limit switch of double-throw type is used and a capacitor is arranged to be charged via the limit switch.
  • the capacitor is normally discharged and is charged when the clutch assumes a disengaged state, thereby producing a trigger pulse used for making a short circuit for the motor, only when the capacitor is not fully charged.
  • the capacitor is normally charged, and is discharged when the clutch assumes a disengaged state, thereby producing a trigger pulse used for making a short circuit for the motor.
  • a circuit arrangement for an electrical tool with a clutch comprising: a power switch for supplying a motor of said tool with electrical power; a limit switch responsive to said clutch which assumes first and second states for selectively transmitting power fed through said power switch; a switching circuit of self-holding type responsive to said limit switch for short-circuiting said motor when said clutch is in a predetermined state, said switching circuit being powered through said power switch; and means responsive to said limit switch for preventing said switching circuit from making a short circuit with respect to said motor, said means having a capacitor arranged to be charged through said limit switch.
  • a circuit arrangement for an electrical tool with a clutch comprising: a power switch of double-throw type, for assuming a first state for supplying a motor of said tool with electrical power and a second state for making a short circuit for said motor; a limit switch of double-throw type responsive to said clutch, for assuming a first state for receiving power source voltage through said power switch when said power switch is in said first state, and a second state in which said power source voltage is not received; a switching circuit of double-throw type for assuming a first state normally for supplying said motor with electrical power and a second state for short-circuiting said motor; a capacitor connected between said limit switch and said switching circuit for causing said switching circuit to assume said second state only when said limit switch is in said first state and said capacitor is in other than fully-charged state; and a discharging circuit connected to said limit switch and to said capacitor so that said capacitor is discharged when said limit switch assumes said second state.
  • FIGS. 1 and 2 are explanatory cross-sectional views of a clutch used in electrical tools according to the present invention
  • FIG. 3 is a schematic circuit diagram of an embodiment of the present invention.
  • FIG. 4 is a schematic circuit diagram of another embodiment of the present invention.
  • FIG. 1 shows a state of driving a screw, nut or the like in a tightening direction.
  • a motor shaft 2 coupled with an unshown electrical motor rotates
  • a fixed clutch 1 secured to the motor shaft 2 also rotates.
  • a movable clutch 3 is attached to a driven shaft 5 via ball keys 4, and is slidable in the axial direction of the driven shaft 5 and rotates together with the driven shaft 5.
  • the movable clutch 3 is pressed toward a fixed key 8 secured to the fixed clutch 1 by way of a coil spring 6 which is attached to the movable clutch 3 via a thrust ball bearing 7.
  • a limit switch 10 is located around the movable clutch 3 such that the limit switch 10 is operated when the movable clutch 3 moves left from the position of FIG. 1.
  • the limit switch 10 is of double-throw type whereas conventional limit switches are of single-throw type.
  • the limit switch 10 has a movable contact "a” and two stationary contacts "b" and “c", and the movable contact "a” is in contact with the stationary contact " c" when the movable clutch 3 is in the position of FIG. 1. Under the condition of FIG.
  • the clutch When the operation of the electrical tool is interrupted, the clutch normally returns to the state of FIG. 1. However, the clutch remains sometimes in the disengaged state of FIG. 2 after the operation of the electrical tool has been interrupted or terminated.
  • the electrical motor cannot be restarted when a power switch is turned on again in the conventional arrangement because a conventional limit switch causes another switching circuit to establish a short-circuit for the motor.
  • the circuit arrangement according to the present invention removes such a drawback so that the motor can be restarted whenever the power switch is turned on.
  • the circuit generally comprises a d.c. power source 11, which may be a battery or a rectifying circuit responsive to an a.c. power source, a power switch 12 of double-throw type, a limit switch 10 of double-throw type, a forward/reverse switch 14, a d.c. motor M, and a switching circuit including a relay circuit 13 and thyristor circuit S which drives the relay circuit 13.
  • a d.c. power source 11 may be a battery or a rectifying circuit responsive to an a.c. power source
  • a power switch 12 of double-throw type a limit switch 10 of double-throw type
  • a forward/reverse switch 14 a d.c. motor M
  • a switching circuit including a relay circuit 13 and thyristor circuit S which drives the relay circuit 13.
  • the power switch 12 comprises a movable contact "a” contactable with either a stationary contact “b” or another stationary contact “c", where the stationary contact "b” is connected to a positive terminal of the power source 11, and the movable contact "a” and the other stationary contact “c” are respectively connected to terminals of the forward/reverse switch 14.
  • the stationary contact "c” is provided for braking the motor M through dynamic braking when the power switch 12 is turned off.
  • the forward/reverse switch 14 is a conventional double-throw, double-pole switch for changing the polarity of supplying voltage to the motor M so that a desired rotational direction is obtained for either tightening or loosening a screw.
  • the limit switch 10 is of the double-throw type as mentioned in the above, and a positive terminal "+” of a capacitor C2 is connected to the movable contact "a" thereof.
  • a negative terminal "-" of the capacitor C2 is connected to the stationary contact "c" and to the anode of a diode D whose cathode is connected via a resistor R2 to the gate of a thyristor SCR of the thyristor circuit S.
  • the thyristor circuit S also comprises a capacitor C1 and a resistor R1 connected in parallel between the gate of the thyristor SCR and ground connected to a negative terminal of the power source 11.
  • the relay circuit 13 comprises a solenoid L which actuates a movable contact "A" thereof on energization.
  • the solenoid L is connected at its one terminal to the movable contact "a" of the power switch 12, and at the other terminal to the anode of the thyristor SCR.
  • the relay has a stationary contact "B” connected to the movable contact "a” of the power switch 12, and another stationary contact “C” connected to ground.
  • the relay circuit 13 is provided for making a short circuit for the motor M when the tightening torque exceeds a predetermined value in the same manner as in conventional circuit arrangements, and the thyristor circuit S is provided for energizing the solenoid L of the relay circuit 13.
  • the thyristor circuit S functioning as a drive circuit for the relay circuit 13, is arranged to be triggered by a trigger pulse fed from the capacitor C2 as will be described in detail hereinafter.
  • the capacitor C2 preferably has a value around 0.1 microfarad when the voltage of the power source 11 is 140 volts.
  • the circuit arrangement of FIG. 3 operates as follows. Before turning on the power switch 12, one of tightening mode and loosening mode is selected by the forward/reverse switch 14 which is manually operable. Normally, the clutch is in the state of FIG. 1 before the power switch 12 is turned on, while respective switches are in the state shown by solid lines in FIG. 3. In detail, the power switch 12 is not yet turned on so that the movable contact "a” thereof is in contact with a stationary contact "c", the movable contact "a” of the limit switch 10 is in contact with the stationary contact "b”, the movable contact "A" of the relay circuit 13 is in contact with the stationary contact "C".
  • the charging of the capacitor C2 starts since current flows via the capacitor C2, the diode D, the resistor R2 and the resistor R1 of the thyristor circuit S.
  • a positive pulse is applied to the gate of the thyristor SCR to turn on the same.
  • the thyristor SCR is rendered conductive causing the energization of the solenoid L of the relay circuit 13. Therefore, the movable contact "A" of the relay circuit 13 is attracted toward the solenoid L so as to be in contact with the stationary contact "B".
  • the movable contact "A" of the relay circuit 13 leaves the stationary contact "C” to cut off the power supply to the motor M.
  • the power switch 12 is manually turned off and thus the movable contact "a” thereof is returned to be in contact with the stationary contact "c". Therefore, the thyristor SCR is turned off to de-energize the solenoid L of the relay circuit 13. Thus, the movable contact "A” of the relay circuit 13 returns to be in contact with the stationary contact "C” to restore its original state. As a result, all the switches are put in the initial state prior to operation.
  • the clutch sometimes stops in the state of FIG. 2 in which the movable key 9 of the movable clutch 3 runs on the fixed key 8 of the fixed clutch 1 to be put in a disengaged state.
  • the movable contact "a" of the limit switch 10 is continuously in contact with the stationary contact "b".
  • the power switch 12 is manually turned off after the operation of the electrical tool. Therefore, the thyristor S is turned off to de-energize solenoid L of the relay circuit 13. Accordingly, the movable contact "A" of the relay circuit 13 returns to the stationary contact "C".
  • the motor M starts rotating without receiving braking force.
  • the movable clutch 3 moves back to the state of FIG. 1
  • the movable contact "a" of the limit switch 10 comes into contact with the stationary contact "c” so that the capacitor C2 is immediately discharged via the discharging circuit 20.
  • the capacitor C2 is now ready for generating a trigger pulse when the clutch is put in the state of FIG. 2 in the same manner as described in the above.
  • the diode D connected in series with the capacitor C2 is provided so that discharging of the capacitor C2 is effected by way of only the discharging circuit 20 connected between the contact "c" of the limit switch 10.
  • the forward/reverse switch 14 has been put in a state illustrated by solid lines so that the driven shaft 5 rotates in a direction of tightening the screw.
  • the stationary contact "b" of the limit switch 10 receives a negative voltage.
  • the capacitor C2 is not charged and no trigger pulse is produced. Accordingly, the thyristor circuit S is not triggered and no dynamic braking is effected in the same manner as in conventional electrical screw drivers or the like.
  • the thyristor SCR receives a trigger pulse only when the capacitor C2 is not fully charged. As a result, the thyristor SCR is prevented from continuously receiving a trigger signal when the clutch is put in the disengaged state of FIG. 2.
  • FIG. 4 shows another embodiment of the present invention.
  • This embodiment differs from the embodiment of FIG. 3 in that the limit switch 10 and the capacitor C1 are provided in a different manner. More specifically, the stationary contact "c" of the limit switch 10 is connected to one terminal of the motor M, and the other stationary contact “b” is directly connected to the gate of the thyristor SCR. Furthermore, the capacitor C1 is interposed between the movable contact "a” and ground. The capacitor C2, the discharging circuit 20, and the diode D of FIG. 3 are not used in this embodiment.
  • This embodiment of FIG. 4 operates as follows.
  • the motor M operates in the condition of FIG. 4 (see solid lines in the forward/reverse switch 14 and the limit switch 10)
  • the capacitor C1 is charged.
  • the movable contact "a" of the limit switch 10 comes into contact with the stationary contact "b”, and therefore the capacitor C1 is discharged via the resistor R1.
  • a trigger pulse is applied to the gate of the thyristor SCR for turning on the same. Consequently, the solenoid L of the relay circuit 13 is energized to make a short circuit for the motor M in the same manner as in the above embodiment of FIG. 3. Assuming that the clutch remains in the disengaged state of FIG.
  • the present invention provides a useful circuit arrangement for an electrical tool with a clutch where the motor can be restarted irrespective of the position of the clutch.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Power Engineering (AREA)
  • Details Of Spanners, Wrenches, And Screw Drivers And Accessories (AREA)
  • Stopping Of Electric Motors (AREA)
US06/629,869 1983-07-12 1984-07-11 Circuit arrangement for electrical tool with clutch Expired - Fee Related US4556831A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP58-127195 1983-07-12
JP58127195A JPS6020870A (ja) 1983-07-12 1983-07-12 クラツチ式電動締付工具の制御方式

Publications (1)

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US4556831A true US4556831A (en) 1985-12-03

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Family Applications (1)

Application Number Title Priority Date Filing Date
US06/629,869 Expired - Fee Related US4556831A (en) 1983-07-12 1984-07-11 Circuit arrangement for electrical tool with clutch

Country Status (3)

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US (1) US4556831A (enrdf_load_stackoverflow)
JP (1) JPS6020870A (enrdf_load_stackoverflow)
DE (1) DE3425570A1 (enrdf_load_stackoverflow)

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4656407A (en) * 1985-06-14 1987-04-07 A.R.A. Manufacturing Company Of Delware, Inc. Electric motor servo control system and method
US4725764A (en) * 1985-04-01 1988-02-16 Bsg-Schalttechnik Gmbh & Co.Kg Switch arrangement
US4934494A (en) * 1988-03-30 1990-06-19 Makita Electric Works, Ltd. Combined locking mechanism and switch especially for power tools
US5237248A (en) * 1991-03-28 1993-08-17 Hitachi Koki Co., Ltd. Control circuit having double-pole double-throw switching device for electrically powered tool
US5705903A (en) * 1996-02-12 1998-01-06 Unicoil, Inc. Electric brake for an alternating current motor
US5914576A (en) * 1995-11-13 1999-06-22 Gec-Marconi Aerospace Inc. Locking devices and control circuitry for permanent magnet electric motors
US6094023A (en) * 1996-05-10 2000-07-25 Ericsson; Hans Birger Method and device for braking an all-mains motor
US6369537B1 (en) * 1998-08-01 2002-04-09 Webasto Karosseriesysteme Gmbh Device for displacing movable parts on motor vehicles
US6733414B2 (en) 2001-01-12 2004-05-11 Milwaukee Electric Tool Corporation Gear assembly for a power tool
US20040130282A1 (en) * 2002-07-23 2004-07-08 Christoph Meyer Retarded electric motor
GB2405822A (en) * 2003-09-11 2005-03-16 Bosch Gmbh Robert Power screwdriver with torque limiting device
US20050116670A1 (en) * 2003-12-01 2005-06-02 Lathrop Todd M. Control circuit for a dual directional direct current motor employing a single alternating current power source
US6906493B1 (en) * 2004-01-20 2005-06-14 Molon Motor And Coil Corporation Electronic brake for motor
US20070145925A1 (en) * 2005-11-04 2007-06-28 Credo Technology Corporation Method and apparatus for providing torque limit feedback in a power drill
US20100163266A1 (en) * 2008-12-26 2010-07-01 Makita Corporation Electric power tools
US20140253003A1 (en) * 2013-03-08 2014-09-11 Jtekt Corporation Motor control unit

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62174874U (enrdf_load_stackoverflow) * 1986-04-25 1987-11-06

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3651389A (en) * 1968-11-09 1972-03-21 Nippon Denso Co Safety device for use with automatic automobile window regulator
US3875487A (en) * 1973-05-01 1975-04-01 Mobil Oil Corp Method and apparatus for motor-starting control
SU788073A1 (ru) * 1978-11-24 1980-12-15 Пензенский Политехнический Институт Ограничитель момента на валу электродвигател
US4354147A (en) * 1980-08-15 1982-10-12 Klaussner Hans Jurgen Drive and control arrangement for a mechanical eccentric press

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1142027B (de) * 1960-05-12 1963-01-03 Christian Dunker Verriegelungsvorrichtung fuer elektrische Schalter
SE399376B (sv) * 1975-11-14 1978-02-13 Atlas Copco Ab Elektriska mutterdragare
JPS59110566A (ja) * 1982-12-15 1984-06-26 清水　俊政 クラツチ式自動制御付き電動ドライバ

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3651389A (en) * 1968-11-09 1972-03-21 Nippon Denso Co Safety device for use with automatic automobile window regulator
US3875487A (en) * 1973-05-01 1975-04-01 Mobil Oil Corp Method and apparatus for motor-starting control
SU788073A1 (ru) * 1978-11-24 1980-12-15 Пензенский Политехнический Институт Ограничитель момента на валу электродвигател
US4354147A (en) * 1980-08-15 1982-10-12 Klaussner Hans Jurgen Drive and control arrangement for a mechanical eccentric press

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4725764A (en) * 1985-04-01 1988-02-16 Bsg-Schalttechnik Gmbh & Co.Kg Switch arrangement
US4656407A (en) * 1985-06-14 1987-04-07 A.R.A. Manufacturing Company Of Delware, Inc. Electric motor servo control system and method
US4934494A (en) * 1988-03-30 1990-06-19 Makita Electric Works, Ltd. Combined locking mechanism and switch especially for power tools
US5237248A (en) * 1991-03-28 1993-08-17 Hitachi Koki Co., Ltd. Control circuit having double-pole double-throw switching device for electrically powered tool
US5914576A (en) * 1995-11-13 1999-06-22 Gec-Marconi Aerospace Inc. Locking devices and control circuitry for permanent magnet electric motors
US5705903A (en) * 1996-02-12 1998-01-06 Unicoil, Inc. Electric brake for an alternating current motor
US6094023A (en) * 1996-05-10 2000-07-25 Ericsson; Hans Birger Method and device for braking an all-mains motor
US6369537B1 (en) * 1998-08-01 2002-04-09 Webasto Karosseriesysteme Gmbh Device for displacing movable parts on motor vehicles
US6733414B2 (en) 2001-01-12 2004-05-11 Milwaukee Electric Tool Corporation Gear assembly for a power tool
US6998804B2 (en) * 2002-07-23 2006-02-14 C. & E. Fein Gmbh & Co. Kg Electric motor with electronic brake
US20040130282A1 (en) * 2002-07-23 2004-07-08 Christoph Meyer Retarded electric motor
GB2405822A (en) * 2003-09-11 2005-03-16 Bosch Gmbh Robert Power screwdriver with torque limiting device
GB2405822B (en) * 2003-09-11 2005-12-21 Bosch Gmbh Robert Cut-out screwdriver
US20050116670A1 (en) * 2003-12-01 2005-06-02 Lathrop Todd M. Control circuit for a dual directional direct current motor employing a single alternating current power source
US7053570B2 (en) * 2003-12-01 2006-05-30 Eaton Corporation Control circuit for a dual directional direct current motor employing a single alternating current power source
AU2004233513B2 (en) * 2003-12-01 2009-06-25 Eaton Corporation Control circuit for a dual directional direct current motor employing a single alternating current power source
US6906493B1 (en) * 2004-01-20 2005-06-14 Molon Motor And Coil Corporation Electronic brake for motor
US20070145925A1 (en) * 2005-11-04 2007-06-28 Credo Technology Corporation Method and apparatus for providing torque limit feedback in a power drill
US7400106B2 (en) * 2005-11-04 2008-07-15 Robert Bosch Gmbh Method and apparatus for providing torque limit feedback in a power drill
US20100163266A1 (en) * 2008-12-26 2010-07-01 Makita Corporation Electric power tools
US20140253003A1 (en) * 2013-03-08 2014-09-11 Jtekt Corporation Motor control unit
CN104038126B (zh) * 2013-03-08 2018-04-27 株式会社捷太格特 电动机控制装置

Also Published As

Publication number Publication date
DE3425570A1 (de) 1985-05-02
JPS6020870A (ja) 1985-02-02
DE3425570C2 (enrdf_load_stackoverflow) 1987-06-19

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Owner name: HITACHI KOKI COMPANY, LIMITED 6-2, 2-CHOME, OOTE-M

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